1. Field of the Invention
The present invention pertains to a method of welding pipe and, in particular, to making the top half of the weld with a welding apparatus at the exterior of the pipe and making the bottom half of the weld within the interior of the pipe.
2. Description of the Related Art
In many pipe welding applications, the pipe cannot be rotated during welding. Welding is done with the pipe stationary in a horizontal, i.e., 5-G position, rotating a welding apparatus around the pipe to make the weld. The direction of gravitational forces changes relative to the welding direction as the weld progresses around the pipe. Because of this, some welding positions are more difficult to weld than others. This is particularly true on the lower half of the pipe, where smaller weld pools are typically used to achieve sound welds with acceptable weld bead profiles on the inside diameter of the pipe. This limits weld deposition rates.
The most difficult positions to make a good weld are between the 4:00 o'clock and 8:00 o'clock positions of the pipe, where the weld is being made overhead. In these positions, gravity tends to pull the molten weld pool away from the inside of the pipe, making it more difficult to maintain full penetration and positive root reinforcement.
It is an object of this invention to make a 5-G weld around the diameter of a pipe causing full penetration of root welds and avoiding weld root defects caused by gravitational forces.